Move iOS and macOS implementations into new apple module (#3756)

Move iOS and macOS implementations to a shared folder called `apple`, to allow
us to reduce the code-duplication between these platforms in the future.

The folder structure is now:
- `src/platform_impl/apple/`
  - `appkit/`
  - `uikit/`
  - `example_shared_file.rs`
  - `mod.rs`

* Add preliminary support for tvOS, watchOS and visionOS
* Reduce duplication in Cargo.toml when specifying dependencies

src/platform_impl/macos/util.rs

@@ -1,27 +0,0 @@
-use tracing::trace;
-
-macro_rules! trace_scope {
-    ($s:literal) => {
-        let _crate = $crate::platform_impl::platform::util::TraceGuard::new(module_path!(), $s);
-    };
-}
-
-pub(crate) struct TraceGuard {
-    module_path: &'static str,
-    called_from_fn: &'static str,
-}
-
-impl TraceGuard {
-    #[inline]
-    pub(crate) fn new(module_path: &'static str, called_from_fn: &'static str) -> Self {
-        trace!(target = module_path, "Triggered `{}`", called_from_fn);
-        Self { module_path, called_from_fn }
-    }
-}
-
-impl Drop for TraceGuard {
-    #[inline]
-    fn drop(&mut self) {
-        trace!(target = self.module_path, "Completed `{}`", self.called_from_fn);
-    }
-}